I just bought a shimano 105 rear hub for a mountain bike and did not know this is for a road bike. I compared them and the only thing I can see that is different is the diameter of the shell. Every thing else for example holes, flange size, width, seems to be the same. Bought item on Ebay so its not returnable, is it worth a try to change the hubs..Pros/ Cons if it fits.. or just purchase a mountain bike hub.
The 105 hub is made for a standard road bike axle length (called over-locknut distance OLD) of 130mm. The standard for MTBs is 135. Its better to get an MTB compatible hub. The 105 is strong-enough for off-road riding, but not extreme stunts. Its just the wrong width.
Did the hub have a wheel attatched? Its unusual to have a 26" rim on a 105 hub.
If not, are you planning to buil up a wheel? Then you should learn a bit more about wheels.
The best thing you can do with that 105 hub is to use it as the basis for a road bike and do some proper cycling